[Pc_Support] Re: 64 bit processor follow up

[Bryan J. Smith <b.j.smith at ieee.org>]

From: Chris Louden <chris.louden at gmail.com>
> Are the P4 6xx series "true" 64 bit processors?

Actually, AMD processors not "true" 64-bit processors.
But then nor was the Digital Alpha, etc...

What AMD64 processors are:  
- 64-bit Integer + 128-bit XMM 3+3 issue ALU+FPU
- PAE52/48-bit register addressing
- 40-bit I/O Memory Management Unit (I/O MMU)
- Split 40-bit EV6 Memory and HyperTransport Addressing

What EMT64 processors are:
- 64-bit Integer + 80-bit FPU87 + 128-bit SSE 2+2+2 ALU+FPU+SSE
- PAE52/48-bit register addressing
- *NO* I/O Memory Management Unit (handled by the AGTL+ "Memory Controller Hub")
- Shared PAE32/32-bit AGTL+ Memory/IO Addressing

Until Intel adopts the same interconnect at Itanium, it will still have several PAE36/32-bit limitations in its hardware platform.
And even Itanium is still a "Shared Bus" (even though they call it a "Scalable Node Architecture").
Only proprietary Itanium implementations of non-Intel design (such as the SGI Altix) break the "front side bottleneck" for serious-$$$.



--
Bryan J. Smith   mailto:b.j.smith at ieee.org